WO2011034115A1

WO2011034115A1 - Dissociation method and dissociation agent for avidin and biotin

Info

Publication number: WO2011034115A1
Application number: PCT/JP2010/066005
Authority: WO
Inventors: 片寄　聡
Original assignee: Jsr株式会社
Priority date: 2009-09-17
Filing date: 2010-09-16
Publication date: 2011-03-24
Also published as: CN102575244B; JP5686098B2; US8685655B2; EP2479268B1; JPWO2011034115A1; US20120171763A1; CN102575244A; EP2479268A1; EP2479268A4

Abstract

Provided are a dissociation method and dissociation agent for avidin or streptavidin and biotin derivatives which make it possible to efficiently isolate a target material in a short time under mild conditions. The dissociation method for avidin or streptavidin and biotin derivatives includes mixing avidin or streptavidin bound with desthiobiotin with a water-soluble polymer with which biotin or a derivative thereof has bound.

Description

Dissociation method and dissociator for avidin and biotin derivative

The present invention relates to a dissociation method and dissociator for avidin or streptavidin and a biotin derivative.

Avidin or streptavidin (hereinafter referred to as “avidin and the like”) has a strong specific affinity with biotin or a biotin derivative, and can easily be bound (mixed between avidin and biotin) when mixed under physiological conditions. A binding substance or a binding between avidin or the like and a biotin derivative is collectively referred to as “ABC binding”) to form a conjugate of avidin or the like and biotin to form a target substance such as a cell (“target A technique for separating the material is also used (Patent Document 1).
For example, an ABC bond is formed by mixing a biotin-labeled probe molecule in which biotin is previously bound to a probe molecule such as an antibody having binding properties with a target substance and an insoluble carrier on which avidin is immobilized under physiological conditions. If the target substance can be captured using this capture carrier, and then the ABC binding or the binding between the probe molecule and the target substance can be cleaved, the target can be captured. It is possible to separate substances (Patent Document 1).

However, since the affinity between avidin or the like and biotin is extremely high, it is very difficult to cleave the ABC bond under physiological conditions, and in order to dissociate the avidin and the biotin derivative, for example, about pH 1.5 Extreme conditions such as treatment with guanidine hydrochloride or boiling with a buffer for SDS polyacrylamide gel electrophoresis to which a reducing agent is added are necessary. For this reason, when targeting a target substance that is damaged by extreme pH, heat, salt concentration, or physical shearing force, such as proteins and cells, the target substance must be retained in a state that retains physiological activity. Separation has generally been difficult.
For this reason, in order to facilitate separation of the target substance, a method using a biotin derivative having a lower affinity for avidin or the like than biotin (Patent Document 2), a method using an avidin variant having a lower affinity for biotin than avidin (patent Document 3) is known. For example, instead of biotin, the above-mentioned capture carrier is prepared using a biotin derivative such as desthiobiotin (Patent Document 2) having a lower affinity for avidin or the like than biotin, and after capturing the target substance, a large amount of biotin There is known a method of cleaving ABC binding and separating a target substance by adding. In this case, biotin is considered to function as a competitive inhibitor for the binding of desthiobiotin and avidin. However, in this method using biotin as a competitive inhibitor, it is difficult to efficiently cleave ABC bonds, and it is difficult to efficiently separate target substances.

Special table 2010-512537 Japanese Patent Laid-Open No. 02-184777 Japanese Patent Laid-Open No. 10-028589

The present invention provides a method for efficiently dissociating avidin or the like and a biotin derivative having an affinity lower than that of biotin in a short time under mild conditions and a dissociator thereof.

Thus, as a result of various studies to find a means for efficiently dissociating avidin and the like and a biotin derivative having a lower affinity than biotin, the present inventors surprisingly found a water-soluble polymer to which biotin and the like are bound. When used as a dissociating agent, it was found that avidin and the like and a biotin derivative having a lower affinity than biotin were dissociated extremely efficiently under mild conditions, and the present invention was completed.

That is, the present invention relates to a conjugate of biotin derivative (1) having a lower affinity for avidin and avidin or a conjugate of streptavidin and biotin derivative (1) (hereinafter collectively referred to as “avidin-biotin complex”). And a biosoluble derivative (1) are dissociated with a biotin or a derivative thereof (2) and a water-soluble polymer (hereinafter referred to as “dissociator”). A method is provided.

The present invention also provides a method for separating a target substance,
(A) a step of mixing a capture carrier and a target substance in an aqueous solvent to obtain a mixed solution 1;
(B) a step of mixing the liquid mixture 1 with a water-soluble polymer to which biotin or a derivative thereof (2) is bound to obtain a liquid mixture 2;
(C) A method including the step of separating the target substance from the mixed solution 2 is provided.
However, the capture carrier is a combination of the following (A) and (B).
(A) Avidin immobilized on an insoluble carrier or streptavidin (B) Affinity immobilized on a substance having specific affinity for a target substance (hereinafter referred to as “probe molecule”) is higher than that of biotin. Low biotin derivative (1)

Furthermore, the present invention provides a dissociator used for dissociating avidin or streptavidin and biotin derivative (1), which contains a water-soluble polymer to which biotin or a derivative thereof (2) is bound.

According to the method of the present invention, the bond between avidin and the biotin derivative (1) can be efficiently cleaved in a short time under mild conditions to dissociate the avidin and the biotin derivative (1). Further, by applying the method to the separation of the target substance, the target substance obtained by binding to the capture carrier can be easily separated. Even when the target substance is unstable with respect to temperature conditions and pH conditions such as proteins and cells, the target substance can be separated while maintaining its activity by using the method of the present invention.

It is a conceptual diagram which shows the state which the support | carrier for capture | acquisition used in 1 aspect of this invention couple | bonded with the target cell.

Hereinafter, the dissociation method and dissociation agent of avidin and the biotin derivative (1) according to an embodiment of the present invention will be specifically described.
(Method of dissociating avidin and biotin derivatives)
The method for dissociating avidin and the like and the biotin derivative (1) according to an embodiment of the present invention includes a step of mixing an avidin-biotin complex and a water-soluble polymer to which biotin or a derivative thereof (2) is bound. The dissociation method of the present invention is usually performed in a solvent containing water as a main component. In that case, the avidin-biotin complex is preferably dissolved in the solvent. However, when the avidin-biotin complex is bound to an insoluble carrier, the avidin-biotin complex is contained in the solvent together with the carrier. May be dispersed.

(Avidin-biotin complex)
The avidin-biotin complex used in the present invention is a conjugate of avidin or streptavidin and a biotin derivative (3) having a lower affinity for avidin than biotin (a compound represented by the following formula (3)). . Here, as avidin or streptavidin, commercially available products can be used, and these may be those obtained by separating and purifying those existing in nature, or artificially produced by genetic engineering techniques. It may be an avidin or a streptavidin derivative modified within a range not losing its ability to bind to biotin. Examples of the derivatives of avidin or streptavidin include chemically modified avidin or streptavidin such as succinylation, and a monomer of avidin or streptavidin which is usually a tetramer.

The biotin derivative (1) is not particularly limited as long as it is a biotin derivative having a lower affinity for avidin than biotin. Avidin and biotin derivative (1) are effectively dissociated by mixing the avidin-biotin complex with a water-soluble polymer to which biotin or its derivative (2) is bound due to its lower affinity for avidin. can do.
Examples of such a biotin derivative (1) include desthiobiotin (a compound represented by the following formula (4)), 2-iminobiotin (a compound represented by the following formula (5)), 3,4- Derivatives that differ from biotin in the cyclic structure portion of biotin such as diaminobiotin (compound represented by the following formula (6)), and chemically modified products thereof.

A lower affinity for avidin than biotin means that the binding constant is one or more orders of magnitude smaller than that of avidin and biotin (10 ¹⁵ M). For example, the binding constant between the compounds represented by the above formulas (4) to (6) and avidin is 10 ⁶ M to 10 ¹³ M.

(Avidin-biotin complex immobilized on an insoluble carrier)
The avidin-biotin complex used in the present invention may be immobilized on an insoluble carrier via avidin or the like. Since the avidin-biotin complex is immobilized on an insoluble carrier, the avidin-biotin complex can be easily separated from the dispersion containing the avidin-biotin complex by a method such as centrifugation or filtration.
The insoluble carrier used for immobilizing avidin and the like is not particularly limited in shape, and examples thereof include organic or inorganic particles, a flat substrate, a substrate having a fine channel, a microwell plate, and the like. Among these, the organic particles are preferably particles made of an organic synthetic polymer mainly composed of polystyrene having an average particle size of 0.5 to 10 μm. Furthermore, the particles are preferably magnetic particles in that they can be separated by magnetism.
Examples of commercially available magnetic particles include Dynabeads M-450 Tosylactivated (manufactured by Invitrogen) and Magnosphere MS300 / Carboxyl (manufactured by JSR Corporation). The magnetic particles are preferably produced according to a known method (for example, see Japanese Patent Publication No. 05-010808 or Japanese Patent Application Laid-Open No. 2007-288133), and can reduce nonspecific adsorption of proteins and cells. .

The method for immobilizing an insoluble carrier such as avidin is not particularly limited, and a known method (for example, see JP-A-2001-158800) can be used. For example, when an insoluble carrier having a carboxyl group on the surface is used, an amide bond is formed by reacting an amino group in a molecule such as avidin with a carboxyl group on the carrier surface in the presence of a dehydrating condensation agent such as water-soluble carbodiimide. By doing so, avidin and the like can be immobilized on an insoluble carrier. In such a method, a dehydration condensing agent may be reacted in advance with the carboxyl group of the carrier, and then avidin or streptavidin may be added and reacted.

(Capture carrier)
The avidin-biotin complex used in the present invention may be a conjugate of the following (A) and (B) (hereinafter referred to as “capture carrier”).
(A) Avidin or streptavidin immobilized on an insoluble carrier (B) Biotin derivative immobilized on a substance having specific affinity for a target substance (hereinafter referred to as “probe molecule”) (1)

Although it does not specifically limit as a probe molecule, For example, in addition to proteins, such as an antibody with respect to a target substance, a lectin, and an enzyme, saccharides etc. are mentioned. The probe molecule has a property capable of specifically binding to the target substance and is bound to the biotin derivative (1). The probe molecule and the biotin derivative (1) may be directly bonded or may be bonded via a spacer.
The biotin derivative (1) immobilized on the probe molecule is a biotin derivative (1) having a lower affinity for avidin than the biotin described in the section on avidin-biotin complex.
The method for binding the biotin derivative (1) to the probe molecule is not particularly limited. For example, a method similar to the method for immobilizing avidin or the like on the surface of the carrier can be used. For example, when using a probe molecule having an amino group, the amide bond is formed by reacting the carboxyl group in the biotin molecule with the amino group in the probe molecule in the presence of a dehydrating condensation agent such as water-soluble carbodiimide. Thus, a biotin-binding probe molecule can be obtained.

By using a separation carrier as the avidin-biotin complex, since the avidin-biotin complex specifically binds to the target substance, the target substance bound to the capture carrier can be specifically separated.
FIG. 1 shows a conceptual diagram of a capture carrier bound to a target substance.

(Target substance)
The target substance is not particularly limited. For example, cells (for example, various cells of bacteria, fungi, animals or plants), viruses, proteins (for example, various antigens or antibodies, enzymes), single-stranded or double-stranded Examples thereof include nucleic acids such as DNA or RNA, steroid lipids such as estrogen, glycolipids, polysaccharides and the like. Specific examples of cells that are target substances (hereinafter referred to as “target cells”) are not particularly limited. For example, normal cells (for example, stem cells such as hematopoietic stem cells, blood cells such as leukocytes, etc.), cancer cells ( For example, circulating cancer cells in peripheral blood derived from breast cancer and lung cancer, exfoliated cancer cells present in stool derived from colon cancer, cancer cells in menstrual blood derived from uterine cancer, Cancer cells derived from bladder cancer or the like present in urine). By the method for separating a target substance of the present invention, the target substance can be efficiently separated.

(Dissociator)
In the method for dissociating avidin and the like and the biotin derivative (1) of the present invention, an avidin-biotin complex is mixed with a water-soluble polymer (hereinafter also referred to as “dissociator”) to which biotin or a derivative thereof (2) is bound. By doing so, the bond between avidin and the biotin derivative (1) can be cleaved, and avidin and the biotin derivative (1) can be dissociated.

The dissociator is most preferably a water-soluble polymer to which biotin is bound.
Examples of biotin derivatives (2) that can be used in the dissociating agent include biocytin (biocytin: biotin-ε-N-lysine; a compound represented by the following formula (7)), biotin-N-hydroxysuccinimide ester (see below). A compound represented by the formula (8)), a derivative represented by the following formula (9) (Biotinyl-3,6,9-trioxaundecanediamine), etc. Examples include derivatives different from biotin in the cyclic structure portion of biotin described in the section on avidin-biotin derivatives. Among these, for the cyclic structure portion of biotin, a derivative having the same structure as biotin is preferable because of its strong affinity with avidin.

In order to dissociate avidin or the like and biotin derivative (1), for example, a dissociating agent may be added to and mixed with a liquid sample containing an avidin-biotin complex under physiological conditions. As physiological conditions, for example, conditions of 20 to 40 ° C., about 1 atm, pH 5 to 9 and the like are preferable.

By using the dissociating agent of the present invention can be dissociated avidin or the like and the biotin derivative (1) efficiently. When a dissociation agent is added to an aqueous sample containing an avidin-biotin complex, avidin contained in the dissociation agent or a derivative thereof (2) competes with the biotin derivative (1) bound to avidin, etc. The biotin derivative (1) can be dissociated. And, the dissociation agent in which biotin or its derivative (2) is bound to the water-soluble polymer is more efficient than biotin or its derivative (2) that is not bound to the water-soluble polymer, although the reason is not necessarily clear. In addition, avidin and the biotin derivative (1) can be dissociated.

The water-soluble polymer is not particularly limited as long as it is a water-soluble polymer and can bind to biotin or a derivative (2) thereof, but it binds to the water-soluble polymer using a carboxyl group possessed by biotin. Water-soluble polymers having functional groups such as amino groups, sulfhydryl groups, and carboxyl groups are preferred. Examples include organic synthetic polymers having reactive functional groups such as amino groups in addition to water-soluble proteins and polysaccharides. The water-soluble proteins, for example, BSA (bovine serum albumin), etc. HSA (human serum albumin) are preferred. Examples of the polysaccharide include CMC (carboxymethyl cellulose) and chitosan. As the organic synthetic polymer having a reactive functional group, for example, synthetic polymers such as PAA (polyacrylic acid) and polyallylamine, and polyamino acids such as polylysine and polyaspartic acid are preferable.

In the present invention, the term "water soluble", when dissolved in a concentration of 1 mg / ml, refers to the property of dissolving without clouding.

Although not particularly limited in molecular weight of the biotin-binding water-soluble polymer is preferably 1,000 to 1,000,000. By setting the molecular weight of the biotin-conjugated water-soluble polymer within the above range, the avidin-biotin complex can be dissociated with high efficiency. The molecular weight of the biotin-conjugated water-soluble polymer can be measured, for example, by gel permeation chromatography.

The average number of molecules of biotin or its derivative (2) bound per molecule of the water-soluble polymer is preferably as much as possible within the range in which the water-solubility is not lost. More preferably, it is more preferably 5 to 1,000, and particularly preferably 10 to 100. The more biotin or its derivative (2) bound per molecule of water-soluble polymer, the higher the dissociation efficiency between avidin and the biotin derivative (1). The average value of the number of molecules of biotin or its derivative (2) bound per molecule of the water-soluble polymer can be measured by the method (HABA method) described in Examples described later.

As a method for binding biotin or a derivative thereof (2) to the water-soluble polymer, for example, biotin or a derivative thereof (2) is reacted with a water-soluble polymer having at least one of a carboxyl group and an amino group. The method of obtaining is mentioned. When the water-soluble polymer contains an amino group, a method of dehydrating and condensing the amino group in the water-soluble polymer and the carboxyl group of biotin can be mentioned. When the water-soluble polymer contains a carboxyl group, a method of dehydrating and condensing the carboxyl group in the water-soluble polymer and the amino group of a biotin derivative having an amino group can be mentioned.

(Method for separating target substances)
The method for separating a target substance of the present invention comprises (a) a step of mixing a capture carrier and a target substance in an aqueous solvent to obtain a mixed liquid 1, and (b) a mixed liquid 1 and biotin or a derivative thereof (2). A step of mixing the water-soluble polymer to which is bound to obtain the mixed solution 2, and (c) a step of separating the target substance from the mixed solution 2. Here, the capture carrier is
(A) Avidin or streptavidin immobilized on an insoluble carrier and (B) a biotin derivative (2) immobilized on a substance having specific affinity for a target substance (hereinafter referred to as “probe molecule”) It is a combination.

(Step of obtaining the liquid mixture 1 by mixing the capture carrier and the target substance in an aqueous solvent)
This step is a step of binding the capture carrier and the target substance. Specifically, by mixing the capture carrier and the target substance, the probe molecule contained in the capture carrier and the target substance or a molecule having affinity with the probe molecule contained in the target substance are specifically bound. .
The capturing carrier and the target substance are as described above. As the aqueous solvent, a solvent containing water having a pH of 5 to 9 as a main solvent is preferable, and a buffer solution such as a phosphate buffer or a Tris buffer is more preferable.
In order to mix the capturing carrier and the target substance, it is preferable to mix the capturing carrier dispersed in the aqueous solvent and the target substance dissolved or dispersed in the same or different aqueous solvent. After mixing, it is preferable to mix at 10 to 40 ° C. for 1 to 60 minutes. By mixing under such conditions, the capture carrier and the target substance are efficiently bound.
The amount of the capture carrier to be mixed can be appropriately adjusted depending on the amount of the target substance contained in the sample.

(The process of obtaining the liquid mixture 2 by mixing the liquid mixture 1 and a water-soluble polymer to which biotin or a derivative thereof is bound)
This step is a step of adding a dissociator to cleave the bond between avidin and the like in the capture carrier and the biotin derivative (1) to dissociate the avidin and the biotin derivative (1). In order to mix the mixed solution 1 and the dissociating agent, it is preferable to mix the dissociating agent solution dissolved in the aqueous solvent and the mixed solution 1. After mixing, it is preferable to mix at 10 to 40 ° C. for 1 to 60 minutes. By mixing under such conditions, avidin and the biotin derivative (1) are efficiently dissociated.
This step may include a step of separating the capture carrier from the liquid mixture 2. When the capture carrier includes magnetic particles, the capture carrier can be easily separated using a magnetic stand.

(Step of separating target substance from liquid mixture 2)
This step is a step of separating the target substance contained in the mixed solution 2, and the target substance is separated from the insoluble carrier or the like by this step. This step can be carried out by any method, but when the capture carrier contains magnetic particles, the capture carrier can be easily separated using a magnetic stand. When the capture carrier does not contain magnetic particles, a method of centrifuging under a centrifugal condition that does not allow the target substance to settle, or a method such as filtering with a filter having a pore size that does not capture the target substance may be used. it can.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Preparation Example 1]: Preparation of desthiobiotin-binding probe molecule (anti-Ep-CAM antibody) 5 mg of desthiobiotin (manufactured by MP Biomedicals) was dissolved in 0.5 ml of dimethyl sulfoxide. In this solution, N-hydroxysuccinimide (NHS) and 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC hydrochloride) were each 5.36 mg (1.2% with respect to the carboxyl group of desthiobiotin). Equivalent) and reacted at room temperature for 60 minutes. An antibody against Ep-CAM, an epithelial specific antigen dissolved in 1 ml of PBS (phosphate buffered saline), was separated from this reaction solution (anti-Ep-CAM antibody: clone Ber-EP4, purchased from Dako International) ) 2 mg, and further reacted at room temperature for 3.5 hours. Unreacted desthiobiotin was removed by ultrafiltration to obtain a desthiobiotin-conjugated anti-Ep-CAM antibody.

[Preparation Example 2]: Preparation of avidin-biotin complex (capture carrier) 1 mg of streptavidin magnetic particles (Invitrogen Dynabeads M-280 Streptavidin) and 2 μg of desthiobiotin-conjugated anti-Ep-CAM antibody obtained in Preparation Example 1 Was taken in a test tube and mixed in PBS for 30 minutes to bind streptavidin and desthiobiotin. Next, magnetic particles are separated from the reaction solution using a magnetic stand, washed 3 times with PBS containing 0.05% Tween 20 to remove unreacted desthiobiotin-binding probe molecules, and desthiobiotin-binding probe molecules. Thus, an avidin-biotin complex (capture carrier) was obtained in which streptavidin and magnetic particles were bound.

[Preparation Example 3]: Preparation of dissociator (1) (synthesis of bovine serum albumin (BSA) conjugated with biotin)
200 mg of biotin (molecular weight: 244.31) was dissolved in 2.76 ml of dimethyl sulfoxide, and 173 mg of NHS and EDC hydrochloride (1.1 equivalent to the carboxyl group of biotin) was added and reacted at room temperature for 60 minutes. 0.508 ml and 1.27 ml were separated from this reaction solution, and 1 g each of BSA (manufactured by SIGMA) was added to a solution in 50 ml of 10 mM phosphate buffer solution (pH 7.0). Reacted for hours. Unreacted biotin was removed by ultrafiltration to obtain water-soluble biotin-bound BSA. As a result, on average, 6 molecules of biotin-bonded dissociator (referred to as BSA-Biotin6) and 10 molecules of biotin-bonded dissociator (referred to as BSA-Biotin10) were obtained per BSA molecule. The amount of biotin bound to BSA was quantified according to the HABA method (4-hydroxyazobenzene-2-carboxylic acid, NM Green, Methods in Enzymology, vol. 18, p418-424, 1970) by Green et al.

[Preparation Example 4]: Preparation of dissociator (2) (synthesis of polyacrylic acid bound with biotin derivative)
0.1 g of polyacrylic acid (PAA, manufactured by Wako Pure Chemical Industries, Ltd.) having a molecular weight of 250,000 is dissolved in 5 ml of 10 mM phosphate buffer solution (pH 7.0), and 133 mg of EDC hydrochloride (based on the carboxyl group of polyacrylic acid) 0.5 equivalent). Subsequently, a dimethyl sulfoxide solution (10 mg / ml) of a compound represented by the formula (7) which is a biotin derivative having an amino group (Biotin-PEO-LC-Amine; manufactured by Thermo Fisher Scientific Co., Ltd.) 835 ml or 1.67 ml was added, and further reacted at room temperature for 3.5 hours. Unreacted biotin was removed by ultrafiltration to obtain water-soluble biotin-conjugated PAA. Quantification of biotin bound to PAA was performed according to the HABA method. As described above, a dissociation agent (referred to as PAA-Biotin15) to which 15 biotin derivatives are bound on average per PAA molecule, and a dissociation agent (referred to as PAA-Biotin40) to bind 40 biotin derivatives on average per PAA molecule. It was.

[Preparation Example 5] Preparation of target cells Remove the medium from the culture dish in which HT-29 cells (target cells) are cultured, add 1 ml of PBS containing 2 mM EDTA, and hold at 37 ° C for 5 minutes to remove the cells from the culture dish. After peeling, the cells were separated into single cells by pipetting and diluted with PBS to obtain a cell dispersion having a cell concentration of 2.0 × 10 ⁵ cells / ml. HT-29 cells express Ep-CAM antigen.

[Measurement of cell number]
The number of cells was determined by measuring the amount of genomic DNA by quantitative PCR.
(1) Measurement of the number of cells bound to the capture carrier 0.8 mg / ml Proteinase K (proteolytic enzyme; manufactured by QIAGEN) in the total amount of the capture carrier and target cell conjugate obtained in each Example / Comparative Example 50 μl of 10 mM Tris-HCl buffer (pH 8.3) was added and heated at 55 ° C. for 15 minutes to elute the DNA. Subsequently, Proteinase K was inactivated by heating at 95 ° C. for 20 minutes. 20 μl of the obtained DNA solution was added to 30 μl of a cocktail for quantitative PCR (Roche, using FastStart Taq), and quantitative PCR was performed. For the calibration curve, a DNA solution recovered from a certain number of cells by the same method was used. As an apparatus for quantitative PCR, Applied Biosystems 7500 Real-Time PCR System was used.
(2) Measurement of the number of cells separated from the capture carrier Obtained by using a dissociator (biotin in the comparative example) in each of the examples and comparative examples instead of the total amount of the capture carrier and target cell conjugate The number of cells in the total amount of the cell dispersion after dissociation was measured in the same manner as the measurement of the number of cells bound to the capture carrier except that 100 μl in the total amount of the cell dispersion after dissociation was 250 μm.

[Dissociation efficiency]
The dissociation efficiency between avidin and the biotin derivative was determined by the following equation.
Dissociation efficiency (%) = number of cells separated from capture carrier ÷ number of cells bound to capture carrier × 100

[Example 1]
Each 1 mg of the capture carrier obtained in Preparation Example 2 was placed in a test tube and dispersed in 1 ml of PBS containing 0.6% by mass citric acid and 0.5% by mass BSA to obtain a capture carrier solution. To this carrier solution for capture, 50 μl of the cell dispersion obtained in Preparation Example 5 was added and mixed at 4 ° C. for 30 minutes to bind the carrier for capture and HT-29 cells. The capture carrier was then separated using a magnetic stand and washed three times with PBS to separate target cells bound to the capture carrier from unbound cells and other solute components. When the number of cells bound to the separated capture carrier was measured, it was 8,500 cells, 85% of the cells used in the examples.
To the capture carrier bound to the target cells, 250 μl of 0.2 mass% BSA-Biotin 6 PBS solution obtained in Preparation Example 3 was added, and gently mixed for 20 minutes at room temperature. Thereafter, the particles were separated using a magnetic stand, and dissociated HT-29 cells in the supernatant were recovered. When observed with an optical microscope, the cells in the supernatant were present while maintaining their morphology.
Table 1 shows the dissociation efficiency of the target cells. In Table 1, “the concentration of biotin in the dissociation solution” is a value of mass% of biotin calculated from the concentration of the dissociator and the degree of biotinylation of the dissociator.

[Examples 2 to 4]
The dissociation efficiency was determined in the same manner as in Example 1 except that the dissociating agent shown in Table 1 was used instead of BSA-Biotin6.

[Comparative Example 1]
Dissociation efficiency was determined in the same manner as in Example 1 except that a PBS solution of 10 mM biotin was used instead of the PBS solution of 0.2% by mass BSA-Biotin6.

As shown in Table 1, in Examples 1 to 4 using a water-soluble polymer to which biotin was bound as a dissociating agent, compared with Comparative Example 1 using biotin instead of the dissociating agent, In spite of the extremely small biotin concentration, it was confirmed that avidin and the like and biotin derivatives can be dissociated and the target cells can be separated with extremely high efficiency.

Claims

A conjugate of biotin derivative (1) having a lower affinity for avidin and avidin or a conjugate of streptavidin and biotin derivative (1) (hereinafter collectively referred to as “avidin-biotin complex”); A method of dissociating avidin or streptavidin and biotin derivative (1), comprising a step of mixing a water-soluble polymer (hereinafter referred to as “dissociator”) to which biotin or a derivative thereof (2) is bound.
The method according to claim 1, wherein the biotin derivative (1) is a derivative different from biotin in a cyclic structure portion of biotin.
The method according to claim 2, wherein the biotin derivative (1) is at least one selected from desthiobiotin, 2-iminobiotin, and 3,4-diaminobiotin.
The method according to any one of claims 1 to 3, wherein the dissociator has a molecular weight of 1,000 to 1,000,000 as a polystyrene-equivalent number average molecular weight measured by gel permeation chromatography.
The method according to any one of claims 1 to 4, wherein the dissociator is a water-soluble polymer having an average of 2 to 2,000 biotin or a derivative thereof (2) bound thereto per molecule.
The method according to any one of claims 1 to 5, wherein the dissociator is a conjugate of biotin or a derivative thereof (2) with any one of a water-soluble protein, a water-soluble polysaccharide or a water-soluble organic synthetic polymer.
The method according to any one of claims 1 to 6, wherein the biotin derivative (2) is a derivative having the same structure as biotin with respect to the cyclic structure portion of biotin.
The method according to any one of claims 1 to 7, wherein the avidin-biotin complex is a conjugate of avidin or streptavidin immobilized on an insoluble carrier and a biotin derivative.
A method for separating a target substance,
A step of mixing a capture carrier and a target substance in an aqueous solvent to obtain a mixed solution 1;
A step of mixing the liquid mixture 1 with a water-soluble polymer to which biotin or a derivative thereof (2) is bound to obtain a liquid mixture 2;
A method comprising a step of separating a target substance from the liquid mixture 2.
However, the capture carrier is a combination of the following (A) and (B).
(A) Avidin immobilized on an insoluble carrier or streptavidin (B) Affinity immobilized on a substance having specific affinity for a target substance (hereinafter referred to as “probe molecule”) is higher than that of biotin. Low biotin derivative (1)
The method according to claim 9, wherein the target substance is a cell.
A dissociator used to dissociate avidin or streptavidin and biotin derivative (1), which contains a water-soluble polymer to which biotin or its derivative (2) is bound.